Internal combustion engines mounted in vehicles, such as automobiles, are demanded to be improved in fuel economy and output. To satisfy such demands, internal combustion engines having a variable valve timing mechanism, which varies the valve timing of engine valves such as intake valves and exhaust valves, have been put to practical use.
In such engines, to selectively supply and drain oil to and from the variable valve timing mechanism, a movable member of the mechanism fixed to an end portion of a camshaft is operated to change the rotational phase of the camshaft relative to the crankshaft. This varies the valve timing in the engines. The variable valve timing mechanism includes a lock mechanism for selectively prohibiting and permitting operation of the movable member. To selectively supply and drain oil to and from the lock mechanism, the lock mechanism performs prohibiting operation for prohibiting the operation of the movable member of the variable valve timing mechanism or permitting operation for permitting the operation of the movable member.
Oil is selectively supplied to and drained from the variable valve timing mechanism and the lock mechanism through a plurality of oil lines, which configure hydraulic circuits connecting the respective mechanisms to an oil pump. An oil control valve is arranged in each of the oil lines of the hydraulic circuits to change the supply/drainage modes of oil through the oil line for the variable valve timing mechanism and the lock mechanism. By changing the oil supply/drainage modes for the variable valve timing mechanism and the lock mechanism through the oil control valves, the movable member of the variable valve timing mechanism is operated and the lock mechanism is caused to perform the prohibiting and permitting operations.
The oil control valve includes a cylindrical housing and a spool valve as described in, for example, Patent Document 1. The housing has a plurality of ports connected to the variable valve timing mechanism and the lock mechanism.
The spool valve is arranged in the housing and movable in the axial direction. The position of the spool valve is adjusted in the axial direction to selectively open and close the ports by means of a valve body of the spool valve. This changes the oil supply/drainage modes for the variable valve timing mechanism and the lock mechanism. In the oil control valve described in Patent Document 1, a passage through which oil flows into the spool valve extends in the axial direction of the spool valve. Oil is selectively supplied to and drained from the variable valve timing mechanism via the passage.